Filter cleaning system and method

ABSTRACT

The present invention discloses a method for self-cleaning filters without having to open the filter housing. Wash nozzles are integrated with the filter housings such that when the filters are clogged, both back-wash and regular washing can be performed with practically no down time. Moreover, without opening the filter housing, the hazardous components of the fluid to be filtered can be contained and dealt with before they escape the filter housing, thereby significantly reduces the environmental impact and harm to the working crew.

PRIOR RELATED APPLICATIONS

This invention claims priority to U.S. 61/594,544, filed on Feb. 3, 2012and Ser. No. 13/758,636, filed on Feb. 4, 2013, each of which isincorporated by reference in its entirety herein for all purposes.

FEDERALLY SPONSORED RESEARCH STATEMENT

Not applicable.

FIELD OF THE DISCLOSURE

The disclosure generally relates to a system and method forself-cleaning a filter, and more particularly to a system and method forself-cleaning a filter with a nozzle integrated to the filter housingsuch that the filter can be cleaned without opening the filter housing.

BACKGROUND OF THE DISCLOSURE

Industrial filtration systems generally comprise multiple cartridgefilters located within corresponding filter housings, and fluids to befiltered (influents) are supplied to the filter housings for the removalof debris, contaminants and particles. These cartridge filters generallyhave a cylinder shape with a hollow core. Influents are supplied to thehollow core and flowing outwards through the media of the cartridgefilters, leaving debris, contaminants and particles at the surface ofthe media. After conducting such fluid processing for a period of time,the debris and particles will accumulate and clog the filter media,causing the drop of filter efficiency. In worse situations, a cake mayaggregate at the inner surface of the filter cartridge and the filterwill not function. Therefore, the cartridge must be cleaned and/orreplaced after a period of operation. The cleaning of a filter generallyinvolves shutting down the filtration operation, removing the cartridge,and manually spraying the surface to remove the residue so collected.

Another often performed filter cleaning procedure is called “backwash,”where the fluid flow within the filter housing is reversed, and theaccumulated debris and particles can be washed by the fluid and drained.However, such backwash procedure suffers a drawback in that the flow ofthe backwash fluid may not be strong enough to remove or blast theaggregated particulate material or debris on the filter.

WO2009114128 discloses a spraying device that can move along a filtersurface to emit a jet of cleaning fluid to remove residue from thefilter surface. Specifically, the nozzle can move along the length of afilter cartridge to spray the cleaning fluid at the surface of thecartridge. However, such design fails to take into consideration thepossible liquid/gas escape during cleaning, which may cause health andenvironmental concern when the influent contains hazardous components.Furthermore, the design cannot be used with a backwash cycle to improvethe cleaning efficiency.

Therefore, there is a need for a filter cleaning apparatus and methodthat is also able to work in combination with a backwash operation toimprove the cleaning efficiency.

SUMMARY OF THE DISCLOSURE

The present invention relates to an apparatus for cleaning a filterwithin a filter housing without the need to first remove the filter fromthe filter housing. Specifically, the present invention discloses a washnozzle integrated with the filter housing in a cylinder mounted on thefilter housing so that the cylinder can move the wash nozzle up and downinside the filter housing within the hollow core of the filtercartridge. Moreover, the wash nozzle is connected to a source of washfluid through a wash pipe, which is concentrically surrounded by a purgepipe that connects to a drain for purging the fluid and debris duringbackwash stage. A gas injection inlet is also provided for introducing apressurized gas that causes turbulence inside the filter housing to“bubble off” (dislodge) the accumulated solids on the filter, especiallythe inner surface of the hollow core. A purge inlet is provided near thewash nozzle. Sealing mechanism is provided in the system especiallywhere the cylinder is connected to the filter housing to prevent leakingthat hinders regular filtration operation.

The present invention also provides a method for self-cleaning a filtercartridge within a filter housing without opening the filter housing. Awash nozzle is integrated to the filter housing by a cylinder, a gasinjection inlet is provided on the filter housing, and the methodcomprises closing the fluid inlet by terminating the fluid inlet to theinlet housing; closing the drain to the filter housing so that thefilter housing is filled with fluid; initiating a back-wash byintroducing a high-pressure gas into the interior of the filter housingthrough the gas injection inlet at a pressure capable of creatingturbulence that will dislodge particulate matter or debris from the coreof the filter while positioning the wash nozzle at proper locationinside the filter housing; and forcing the fluid out of the filterhousing with the gas whereby the particulate matters from the interiorof the filter cartridge is purged from the filter housing through thepurge pipe near the wash nozzle.

This invention also provides a method for self-cleaning the filtercartridge without opening the filter housing, in which the filtercartridge has a hollow core and the filter housing further comprises afluid inlet connected to the hollow core, and a wash nozzle and washpipe mounted on the filter housing capable of traveling through thehollow core of the filter cartridge. The method comprises the steps of:closing the fluid inlet to the filter housing, washing the filtercartridge by spraying a high-pressure wash fluid from the wash nozzle tobreak the particulate build-up on the hollow core; and draining the washfluid and debris from the fluid inlet by switching on a drain valvefluidly connected to the fluid inlet, wherein the drain valve directsthe fluid from the fluid inlet to a drain pipe.

A processor with sensors can detect pressure build up within the filterhousing to determine the initiation of the self-cleaning process. Aprocessor can control the backwash and washing process using sensors todetect fluid levels and operation of the apparatus.

As used herein, a “pressurized gas” means a gas having a pressure equalto or greater than 20 psi. The exact pressure used may be adjusted basedon system design and depending upon the type of particulate matter ordebris being filtered, but in any case sufficient to dislodgeparticulate matter or debris from the filter core.

As used herein, a “high-pressure fluid” means a fluid sprayed by thenozzle at a pressure equal to or greater than 100 psi. The exactpressure used may be adjusted based on system design and depending uponthe type of particulate matter or debris being filtered, but in any casesufficient to clean the inside of the filter core.

As used herein, “influent” means the fluid to be introduced to andfiltered by the filter.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims or the specification means one or more thanone, unless the context dictates otherwise.

The term “about” means the stated value plus or minus the margin oferror of measurement or plus or minus 10% if no method of measurement isindicated.

The use of the term “or” in the claims is used to mean “and/or” unlessexplicitly indicated to refer to alternatives only or if thealternatives are mutually exclusive.

The terms “comprise”, “have”, “include” and “contain” (and theirvariants) are open-ended linking verbs and allow the addition of otherelements when used in a claim.

The phrase “consisting of” is closed, and excludes all additionalelements.

The phrase “consisting essentially of” excludes additional materialelements, but allows the inclusions of non-material elements that do notsubstantially change the nature of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of the filter housing and the placement washnozzle assembly during filtration stage with the arrows indicating flowduring filtration.

FIG. 2 is a detail cross-sectional view of the purge inlet near the washnozzle.

FIG. 3 is a detail cross-sectional view of the top of the wash pipeassembly showing the purge pipe and the wash pipe connections.

FIGS. 4A-C are cross-sectional views of the backwash stages.

FIGS. 5A-C are cross-sectional views of washing stages.

FIG. 6A is a schematic cross-sectional view of the system where thecylinder is fully extended and the wash nozzle is at the top of thefilter housing and 6B is a schematic cross-section with cylinder in thedown position.

FIG. 7 is a cross-sectional view of the present invention being used intwo or more filter housings and wash assemblies.

FIGS. 8A-B combined are a flow chart illustrating the basic logics ofthe method of this invention.

DETAILED DESCRIPTION

The invention is a novel system and method for self-cleaning filtercartridges without opening the filter housing. In one aspect of thisinvention, a system is provided for cleaning a filter cartridge locatedwithin a filter housing, the filter cartridge having a hollow core, thesystem comprising: a) a wash nozzle integrated in a filter housing, thewash nozzle on a movable cylinder mounted on top of the filter housing,wherein the wash nozzle is fluidly coupled to a source of wash fluidthrough a wash pipe located in the cylinder within the hollow core ofthe filter cartridge and capable of moving vertically within the hollowcore by raising and lowering the cylinder; b) a purge pipeconcentrically surrounds the wash pipe and forms a purge inlet to forman annular space around the wash pipe capable of fluid travel andterminates near the wash nozzle; c) the filter housing having a fluidinlet for introducing a fluid to be filtered, and a fluid outlet fordraining filtered fluid, wherein the fluid inlet is fluidly coupled tothe hollow core of the filter cartridge; and d) a processor controllingthe movement of the wash nozzle.

In another aspect of this invention, there is provided a method forself-cleaning a filter cartridge located within a filter housing withoutopening the filter housing, the filter cartridge having a fluid outlet,a hollow core fluidly connected to a fluid inlet of the filter housing,a gas injection inlet, a wash nozzle and purge pipe mounted on thefilter housing in a cylinder on top of the filter housing, the purgepipe having a purge inlet, a position sensor for detecting positions ofsaid purge inlet, and a pressure sensor for detecting pressuredifferences across the filter cartridge, a fluid level sensor detectingthe fluid level inside the filter housing, and a processor operablycoupled with said fluid level sensor, said position sensor and saidpressure sensor for receiving fluid level information from said fluidlevel sensor and determining the position of said purge inlet, andcontrolling the movement of the wash nozzle, the method comprising thesteps of the method comprising the steps of: a) terminating the fluidinlet to the filter housing; b) closing the fluid outlet to the filterso that the filter housing is filled with fluid; c) placing the washnozzle and the purge pipe at the top of the filter housing; d)initiating a back-wash by introducing a high-pressure gas into theinterior of the filter housing; and e) forcing the fluid out of thefilter housing with the gas with particulate matter from the interior ofthe filter cartridge through the purge pipe.

In yet another embodiment of this invention, there is provided a methodfor self-cleaning a filter cartridge located within a filter housingwithout opening the filter housing, the filter cartridge having a hollowcore, the filter housing having a fluid inlet for introducing theinfluent, and a wash nozzle and wash pipe mounted on the filter housingcapable of traveling through the core of the filter cartridge, themethod comprising the steps of: a) closing the fluid inlet to the filterhousing; b) washing the filter cartridge by spraying a high pressurewash fluid introduced through the wash nozzle to break the particulatebuild-up on the hollow core; and c) draining the wash fluid and debrisfrom the filter housing through the filter inlet.

In still another aspect of this invention, there is provided a methodfor self-cleaning a filter cartridge located within a filter housingwithout opening the filter housing, the method comprising the steps of:a) closing a fluid inlet to the filter housing so that the filterhousing is substantially full of fluid; b) gradually introducingpressurized gas into the filter housing such that the gas createsturbulence that will dislodge particulate matter from the interior ofthe filter core; c) backwashing the filter core by purging the fluidinside the filter housing and the dislodged particulate matter byproviding a purge exit from the filter housing utilizing the force ofthe pressurized gas; d) terminating the backwashing by cessation ofintroduction of pressurized gas in the filter housing and closing thepurge exit; e) washing the filter cartridge by spraying a high-pressurewash fluid to the interior of the filter core to remove any additionalparticulate matter; and f) draining the wash fluid with any particulatematter from the filter housing.

In one embodiment, the purge pipe is not in fluid communication with thewash pipe, and the purge pipe is fluidly connected to a purge drainpipe.

In one embodiment, the fluid inlet is connected to an inlet valve and adrain valve, both of which are operably connected to the processor,which controls the opening and closing of the valves. The fluid outletis fluidly connected to an outlet valve that is also controlled by theprocessor.

In one embodiment, the fluid housing further comprises a gas injectioninlet for introducing a pressurized gas, which creates turbulence in thefilter housing and forces the fluid through the annular space betweenthe wash pipe and the purge pipe.

In one embodiment, the method also includes detecting the pressuredifference during the filtration process to determine when to start theself-cleaning method when the pressure difference reaches apredetermined value. The method also includes detecting the fluid levelinside the filter housing and lowering the purge pipe at a positionbelow the fluid level inside the filter cartridge as the fluid is forcedout of the filter housing.

In one embodiment, the method also includes, during backwash, moving thewash nozzle from the top to the bottom of the filter housing whenpurging fluid, thereby completing a backpulse. The method also includes,during washing, moving the wash nozzle from the bottom to the top of thefilter housing and then back to the bottom, thereby completing a washstroke. In one embodiment, the number of backpulses and wash strokes ispreselected depending on the degree of clogging and the nature of thedeposited particulate matter.

From here on, detailed explanation of the system and method of thisinvention will be made with reference to the drawings. The followingexamples are intended to be illustrative only, and not unduly limit thescope of the appended claims.

Referring to FIG. 1, which shows the wash nozzle assembly 110 integratedwith a filter housing 101. Filter cartridges 104, 105 are located withinthe filter housing 101, although more than two cartridges can be used.Also, if desired only one cartridge can be used. The filter cartridgeshave connected hollow core 103 that is fluidly coupled with a fluidinlet 122 at the bottom of the filter housing 101. The filter cartridgesare connected with a fluid tight seal 106. The fluid inlet 122 isfurther connected to an inlet valve 124 and a drain valve (not shown).During filtration stage, the inlet valve will open to allow a fluid tobe filtered being supplied to the filter through the fluid inlet 122.During washing stage, as discussed later, the drain valve will open suchthat the wash fluid and debris can be drained through the fluid inlet.

The filter housing further comprises a fluid outlet 120, which isfurther connected to an outlet valve (not shown). During the filtrationstage when the fluid enters core 103 under pressure, the outlet valve isopen such that the filtered fluid can exit the filter housing throughthe fluid outlet 120.

The wash nozzle 110 is integrated with the filter housing through acylinder 108 mounted on the top cover 107 of the housing 101. The washnozzle 110 is coupled to a wash tube 114 that is concentricallysurrounded by a purge tube 112. Both the wash tube 114 and purge tube112 are fixed to the top of cylinder 108, such that the cylinder canmove with the wash nozzle along the hollow core 103. The cylinder ispreferably pneumatically operated, with the pneumatic fluid supplied tothe cylinder. In FIG. 1 two pneumatic fluid inlets 109 a, 109 b areshown.

Details of the wash nozzle are shown in FIG. 2, to further illustratethe annular purge inlet 115 near the wash nozzle 110. As discussedabove, the wash nozzle 110 is connected to a wash pipe 114 that issurrounded by a purge pipe 112. Toward the nozzle 110, the purge pipe112 is a bit shorter than the wash pipe 114 such that an annular opening115 is present that serves as a purge inlet during back-washing stage.It is noted that the annular space between the wash pipe 114 and purgepipe 112 is not in fluid communication with the core of wash pipe 114such that the fluid in each space will not be mixed.

Also referring to FIG. 3, which shows the downstream/upstream pipingconnection for purge pipe 112 and wash pipe 114. As shown in the figure,wash pipe 114 is connected to a path 118 that further connects to a washfluid valve (not shown) and a wash fluid source. The purge pipe 112 isconnected to a purge path 116 that further connects to a purge valve anda drain pipe. The functionalities of these pipes and valves will bediscussed in further detail below.

Referring back to FIG. 1, the filter housing 101 also comprises a gasinlet 102 for introducing high-pressure air or gas during the back-washstage. As shown in the figure, the wash nozzle 110 rests at the bottomof the filter housing inside the hollow core. This is the preferredposition for the wash nozzle 110 during especially the filtration stage,because the cylinders are in the lowered, more stable position.

The system further comprises a processor (not shown) for controlling allthe valves, the movement of the wash nozzle, and the gas injection. Thesystem also comprises fluid level sensors for detecting the fluid levelinside the filter housing, pressure sensors for detecting the pressuredifference between the inside and outside of the filter cartridge, andposition sensors for detecting the position of the wash nozzle. Thesesensors are also operably connected to the processor. The embodiments ofthe features are well known in the art and discussed below in detail ofthe operation.

Referring to FIG. 6A, which shows the cylinder 150 fully extended andthe wash nozzle 110 is therefore at the top of the filter housing 101within the hollow core 103. In FIG. 6B, the cylinder 150 is fullyretracted and the wash nozzle 110 is therefore at the bottom of thefilter housing 101 within the hollow core 103. The cylinder ispreferably pneumatically operated with seals (not shown) preventing thegas and/or fluid from escaping the filter housing.

With configuration of the present invention, especially the feature thatthe wash nozzle is integrated within the filter housing, whenever acleaning of the filter cartridge is necessary, there is no need to openthe housing and remove the filter cartridge for cleaning as conventionaldesign, which would cause significant downtime for the filtrationoperation and increase and operational cost. As explained below, thebackwash and washing stages of the present invention ensures thesatisfactory cleaning without the downtime. Furthermore, in the casewhere the fluid to be filtered contains hazardous gas or particles, suchas greenhouse gases, the present invention effectively prevents thosegases or particles from escaping the filter housing into the atmosphere.This feature has significant application for a greener and saferenvironment.

Filtration Stage

Referring back to FIG. 1, which shows the filter system of the presentduring regular filtration operation. The processor opens the inlet valve124 such that the fluid to be filtered can enter the filter housingthrough the fluid inlet 122. The arrows indicate the direction of thefluid to be filtered. After the fluid enters the filter housing, it willflow radically outward from the hollow core 103 to pass through thefilter medium 105. As noted above, the wash nozzle 110 is lowered to thebottom of the filter housing for better stability.

The particles or other impurities in the fluid cannot pass through thefilter medium 105 and therefore remain on the surface of the hollow core103. After filtering for a period of time, the accumulated particles andimpurities aggregate to block and clog the available passageway forfluid in the filter. As clogging worsens, the pressure differencebetween the hollow core and outside of the filter will increase, andwhen the pressure difference reaches a detectable predetermined maximum,self-cleaning can be activated.

Back-Wash Stage

Referring now to FIGS. 4A-C, which illustrates the back-wash stage ofthe present invention. It is called the “back-wash” because the fluid isnow flowing in the direction opposite to the filtration stage. The fluidinlet 122 from the filter housing is closed, as is the fluid outlet forfiltered fluid. Referring to FIG. 4A, which shows the beginning of theback-wash stage. As shown in the figure, the wash nozzle 110 is firstraised to the top of the filter housing 101, while the filter housing isfilled with air through inlet 102 and creates pressure and turbulence onthe fluid inside the filter. This forces fluid and particles from theinside of the filter through the annular purge inlet 115 and out of thepurge pipe 116 as discussed below. The position sensor and fluid levelsensor detects the position of the wash nozzle 110 and the fluid levelinside the filter housing, respectively. The processor ensures that thewash nozzle 110 and the purge inlet 115 stays below the fluid levelduring the backwash stage. In this embodiment the wash fluid is water,but other wash fluids are possible, depending on the accumulated solidsto be cleaned.

High pressure air is then injected into the filter housing through thegas inlet 102. Although in this embodiment air is used, otherhigh-pressure gas can also be used. The high pressure air will causeviolent turbulence in the water inside the filter housing, especially inthe hollow core, and thereby knocking off a portion of solidsaccumulated on the inner surface of the hollow core. At the same time,the processor will open the purge valve that connects to the purge pipe112 and the purge inlet 115, thereby providing a low pressure exit. Thehigh pressure air and the turbulent water will naturally flow to the lowpressure exit, and thereby drain by the purge pipe.

As shown in FIG. 4B, the water level drops with the water being drainedthrough the purge pipe. The injection of high pressure air continues andfurther removes solids accumulated on the hollow core. The empty spaceabove the water level will be occupied by high pressure air whichfurther pushes the water to leave through the purge pipe. FIG. 4C showsthat the water level continues to drop. The back-wash stage willcomplete when the position sensor senses that the wash nozzle reachesthe bottom of the filter housing. At that point the processor will stopair injection and close the purge valve.

Washing Stage

Referring to FIGS. 5A-C, which shows the washing stage of the presentinvention. Generally speaking in the washing stage the wash nozzle 110will travel from bottom to the top of the filter housing and then travelback down to the bottom to complete a “stroke.” However, multiplestrokes of moving up and down the filter housing may also be preferredif that enhances the cleaning efficiency. Referring to FIG. 5A, whichshows the start of the washing stage. The processor opens the wash valveand the discharge valve (both not shown for well known in the field)such that high-pressure wash fluid is supplied to the nozzle 110 throughwash line 118, and the pressurized sprays the interior hollow core toremove any additional particulate accumulated. The processor also opensthe drain valve for draining the water and debris through the fluidinlet. As shown in FIG. 5B, the processor controls the cylinder suchthat the wash nozzle 110 gradually moves up the filter housing 101 alongthe hollow core 103 while spraying high pressure water to continuouslybreak down the accumulated solids. As shown in FIG. 5C, half of thewashing stage cycle is marked by once the position sensor detects thatthe wash nozzle 110 reaches the top of the filter housing 101. Theprocessor then brings the wash nozzle 110 gradually down to the bottom,while still spraying. This cycle, beginning from the wash nozzle 110from the bottom to the top and back to the bottom of the filter housing,is called “one stroke.” If an operator determines that one stroke issufficient to clean the hollow core of the filter cartridge, the washingstage ends and the processor then closes the wash valve, the dischargevalve and the drain valve. If, however, the operator determines thatmore strokes of washing are required, for example because theaccumulated solids are stubborn to be removed, then a stroke counterwill add “1” after each stroke and the washing stage will not stop untilthe stroke count reaches what the operator sets.

Employing the System in Two or More Filters

Referring now to FIG. 7, which shows the system being employed in twoparallel filters. It is to be noted that the system can be employed inan array of filters by the same configurations, and it is for simplicitypurpose to show only two filters. In this figure, two filter housings101, 201 are joined together, and most configurations are the same as inFIG. 1, except that the fluid inlets from both housings are jointlycontrolled by the same inlet valve 144 and drain valve 142, the fluidoutlets from both housings are jointly controlled by the same outletvalve 140, and the gas injection inlets are jointly controlled by thesame gas injection valve 130. This way, the filtration, backwash andwashing stages are activated and controlled together by the sameprocessor for both filters. By this pairing up configuration, theself-cleaning system and method of this invention can easily be employedfor an array of filters.

Method of the Self-Cleaning Method

Referring now to FIGS. 8A and 8B, which combined shows the basic logicsof the filter self-cleaning method of the present invention. In step801, the system is activated in auto-run mode, and the processor willexecute a predetermined plan for self-cleaning, including the backwashstage and washing stage. In step 802, the processor reduces the flowrate to 66% (⅔) of normal setting by partially closing the inlet valve.This is done especially in the filter array setting where some filterhousings are undergoing self-cleaning, and the flow rate is thereforereduced for other on-line filters in order not to overload them. Thenumber is variable depending on the settings and actual conditions. Instep 803, the processor will determine whether the current station(station 1) is locked out. This means that any command sent to thefilter station will be ignored. The station has to be locked out beforethe self-cleaning can begin and there will be no filtration, back-washor washing at this step. If station 1 is locked out, the system proceedsto step 846, where the processor will determine if the next availablefilter station 2 is locked out. This is because the system is configuredsuch that lock-out only occurs when a problem exists in the filterhousing, which makes it unable to take command until the problem isfixed. But if station 1 is not locked out, the system proceeds to step804. With regard to the current station 1, step 846 is a place holder inthe logic, as is station 2.

In step 804, the operator will determine the number of backpulse andstrokes to be performed in the self-cleaning cycle. A backpulse is oneround of backwash, meaning the wash nozzle 110 travels in the backwashstep shown in FIGS. 4A-C from top to bottom once and stops. A stroke isone round of washing, meaning the wash nozzle 110 moving from the bottomof the filter housing to top and back to the bottom. The number ofbackpulse and stroke may vary, depending on how clogged the filter is orthe nature of the solids. If the filter is very clogged or theaccumulated solids are known to be hard to break, the operator maychoose to perform more than one backpulse or more than one stroke forthe cleaning cycle. Whether the predetermined number of backpulse/strokehas been performed will be tracked by the backpulse counter and thestroke counter later in the cycle.

Steps 805 to 814 are related to the backwash stage as illustrated inFIGS. 4A-C. In step 805, the cylinder is raised to move the wash nozzleto the top of the filter housing in preparation of the backwash purge.In step 806, the position sensor will confirm that the cylinder (and thewash nozzle) is raised to the top of the filter housing. In step 807,the system starts preliminarily inject air through the gas injectioninlet for 10 seconds, so as to build up sufficient air pressure insidethe housing, and then in step 808 the gas pressure sensor will determinewhether the gas pressure within the housing is sufficiently high. Asdiscussed above, the gas pressure is important both to create violentturbulence in the fluid to break off the solids, and also pushes thefluid toward the purge pipe. Typically the system will determine a 25psi gas pressure to be sufficient, but it can vary depending ondifferent system requirement, for example in some instance 20 psi may besufficiently high for backwash to proceed. If in step 808 the processordetermines that the pressure is high enough, the system proceeds to step812. If in step 808 the system determines that the gas pressure is nothigh enough, in step 809 the system will continue the preliminary airinjection for another 30 seconds, and check the pressure again in step810. If the pressure is still not reached, the self-cleaning cycle maybe terminated due to the loss of air pressure from external air supply,and the process cannot continue until the problem is addressed. If thepressure is sufficiently high, the system will proceed to step 812,where the processor will open the purge valve for draining the fluidwithin the filter housing, and gradually lower the cylinder to keep thewash nozzle and purge inlet below the fluid level for purging the fluidthrough the purge inlet and purge pipe. In step 813, the position sensorwill confirm that the cylinder and thus the wash nozzle are down to thebottom of the filter housing to complete one “backpulse,” and in step814 the processor stops the air injection and closes the purge valve.

Steps 815 to 821 are preparation for washing stage. In step 815, a fluidlevel sensor at the wash fluid source detects whether enough wash fluidis present. If there is, the system proceeds to step 816, and if not thesystem proceeds to step 820, where the processor determines that no washfluid is available, and closes all the valves and returns to the mainscreen with an “error warning” in step 821. In step 816, wherepreviously determined that sufficient fluid is available, the processorwill open the source and suction valves near the fluid tank. This issimply a designer's choice to have more than one fluid tank as the fluidsource, and each tank has its own source and suction valve for properfluid supply. For example, if one fluid tank is low in reserve thesystem can switch to the other fluid tank for washing while the firsttank is filled up. Alternatively, the system can be equipped with onelarger fluid tank that will not be depleted. Or in another embodiment,the wash fluid is supplied from the already filtered fluid from otherfilters in the filter array such that continuous and replenishing supplyof wash fluid can be accomplished. In step 817, the system willdetermine whether the wash pump is primed, and if it is the systemproceeds to step 822, but if not the system proceeds to step 818. By“primed” it means that there is sufficient fluid in the pump for properfluid supply, and that there is no air present in the pipelines, becauseair will cause pressure drop in the pump, which in turn results ininsufficient pumping. If the system determines that the wash pump is notprimed, the system proceeds to step 818, where the wash pump prime ventwill be opened for 1 minute to vent off the existing air in the washpump and continues to prime the pump. In step 819 the system will checkthe wash pump primer level again, and if it is satisfactory, the systemproceeds to step 822. If the primer level of the wash pump is still nothigh enough, it means no wash fluid is available in step 820, and theprocessor closes all valves and return to main screen with an “error”warning in step 821.

Steps 822 to 834 discuss the washing stage, especially one “stroke” ofwashing. In step 822, the processor opens the discharge valve near thewash pump, the drain valve connected to the fluid inlet, the water washvalve and the wash prime vent. As discussed above, the discharge valveis the result of having two alternate fluid tanks, and may be omitted ifonly one fluid tank is used. The wash prime vent is a vent for excludingair from the wash pump. When all valves are opened, the wash prime ventis closed to prevent air from entering the wash pump. The system thenproceeds to step 823 to start wash pump for 5 seconds for the wash fluidto fill up the pipelines. In step 824, the system checks the outputpressure of the wash pump. If the output pressure is not enough, thesystem proceeds to step 826 with a wash pump error, and stops the pumpand closes all valves in step 827. The self-cleaning cycle will beterminated. If the output pressure is sufficient in step 824, the systemproceeds to step 825, where the cylinder and thus the wash nozzle willbe gradually raised while spraying high-pressure wash fluid to thesurface of the hollow core to break off the solids. The sprayed washfluid and debris is drained through the fluid inlet.

During this washing stage, the wash pump pressure is still continuouslychecked in step 828, and if insufficient pressure is found in step 829,the cycle is again terminated. If the system determines that the pumppressure is sufficient, in step 830 the position sensor determineswhether the cylinder and wash nozzle are all the way to the top of thefilter housing. Once reaching the top of the filter housing, theprocessor lowers the cylinder and the wash nozzle while continuouslyspraying high-pressure wash fluid to the surface of hollow core. Theentire stroke is completed when the cylinder and wash nozzle is at thebottom of the hollow core in step 832, and the processor will confirmthat the cylinder and wash nozzle are down in step 833. In step 834, theprocessor determines whether the predetermined number of strokes hasbeen reached, and if not, the processor will add “1” to the strokecounter and starts over from step 825 to run another stroke. If,however, the predetermined number of strokes is reached, the systemproceeds to step 836 where the wash pump is stopped and all valves areclosed except for the drain valve.

In step 837, additional air is injected for 10 seconds to push anyremaining wash fluid and debris down the fluid inlet. Then, the systemconfirms that low level sensor is off, which means that the filterhousing is now empty. Then air injection is stopped, and the drain valveis closed.

In step 838, the processor determines whether the predetermined numberof backpulse has been reached. If not, in step 839 the processor adds“1” to the backpulse counter, and reset the stroke counter to 1 for thenext cycle. Then in step 840 the processor opens the fluid inlet andvent valves to re-fill the vessels to get ready for the next round ofbackwash. In step 841, the system confirms that the high fluid levelsensors are on, which detect the fluid level inside the filter housing.At this stage water is introduced into the filter housing through thefluid inlet and fill up the filter housing before the air is injected.The air originally existed in the filter housing leaves through thevent. In step 842, the filter housing is full of water, and theprocessor closes the vent valve, and the system is now ready for anotherround of backwash and wash.

In step 843, the system opens the fluid inlet and the system vent,readying the filter housing to be filled. The fluid to be filtered willbe introduced through the fluid inlet, until in step 844 the levelsensors confirms that the filter housing is full, i.e. the high levelsensor in the filter housing is on, while the air leaves through thesystem vent. The processor then closes the vent and open the fluidoutlet, and the filtration can begin.

Based on the discussion above, the self-cleaning filter system andmethod can clean the filter without opening the filter housing. Thissignificantly reduces the cost for cleaning the filters because there ispractically no down time comparing to conventional cleaning because thetime for the self-cleaning backwash and washing cycles is minimalcompared to shutting down the whole filter, open the filter housing,manually remove the filter and clean it and then put it back. Inaddition, in an array of filter housings having the self-cleaningapparatus of the present invention, most filters in the array cancontinue the filtration operation while some filters are being cleanedby the self-cleaning apparatus and method, thereby maintaining theoperation output for the array. More importantly, the self-cleaningsystem assures that the hazardous gases from the filtration process donot escape to the atmosphere and do not harm the working personnel orenvironment.

What is claimed is:
 1. A method for self-cleaning a filter cartridgelocated within a filter housing without opening the filter housing, thefilter cartridge having a fluid outlet and a hollow core fluidlyconnected to a fluid inlet of the filter housing, the method employing asystem for self cleaning cartridge, the system comprising a gasinjection inlet, a wash nozzle and purge pipe mounted on the filterhousing in a cylinder on top of the filter housing, the purge pipehaving a purge inlet, a position sensor for detecting positions of saidpurge inlet, and a pressure sensor for detecting pressure differencesacross the filter cartridge, a fluid level sensor detecting a fluidlevel inside the filter housing, and a processor operably coupled withsaid fluid level sensor, said position sensor and said pressure sensorfor receiving fluid level information from said fluid level sensor anddetermining the position of said purge inlet, and controlling a movementof the wash nozzle, the method comprising the steps of: a) terminatingthe fluid inlet to the filter housing; b) closing the fluid outlet tothe filter so that the filter housing is filled with fluid; c) movingthe wash nozzle and the purge pipe to the top of the filter housing; d)initiating a back-wash by introducing a high-pressure gas into theinterior of the filter housing to dislodge particulate matter from thefilter cartridge; and e) using the high-pressure gas to force the fluidcontaining the particulate matter from the interior of the filtercartridge through the purge pipe, wherein the processor controls amovement of the purge pipe having the purge inlet at a position belowthe fluid level inside the filter housing.
 2. The method of claim 1,comprising an additional step e-l) gradually lowering the purge pipe tomaintain the purge inlet at a position below the fluid level inside thefilter cartridge as the fluid is forced out of the filter housing. 3.The method of claim 1, the method further comprising, prior to step a),detecting the pressure difference during a filtration process todetermine when to start the self-cleaning method.
 4. The method of claim1, wherein said position sensor also detects positions of the washnozzle, said method further comprising the step: f) terminating theback-wash when the position sensor detects that the wash nozzle reachesthe bottom of the filter housing, and wherein the purge pipe is closedupon the termination of the back-wash so fluid cannot travel through thepurge pipe.
 5. The method of claim 1, wherein the high-pressure gasintroduced into the filter housing is capable of creating turbulencethat dislodges particulate matter from the interior of the hollow core.